Flow target for well control apparatus



Nov. 10, 1964 G. CASON 3,156,261

FLOW TARGET FOR WELL CONTROL APPARATUS Filed Aug. 15, 1962 lmxfii 1 ..r I l 59 26 s243 H /qL- ]',/l '32 V w III III I. 5 24 5 FIG 1 3r. as

fez 63 INVENTOR GARLAND CASON United States Patent 3,156,261 FLOW TARGET FGR WELL CONTROL APPARATUS Garland Cason, Barataria, La., assignor to California Research Corporation, San Francisco, Calif., a corporation of Delaware Filed Aug. 13, 1962, Ser. No. 216,556 6 Claims. (Cl. 137800) This invention relates to methods and apparatus for controlling fluid flow from oil and gas wells and, more particularly, this invention relates to an improved flow target for receiving high velocity fluid flow from a production choke in wellhead control apparatus.

In the petroleum producing art it is often necessary or desirable to limit the production of the petroleum fluids from a well to a value less than would result if the well were allowed to flow wide open through the well tubing. A particular example of this is the case where a single well is producing through concentric production strings rom more than one zone and it is desired to maintain production from the zones at a certain ratio. Therefore one or more of the zones must be produced at something less than full capacity. The most common method of controlling production is to install apparatus in the well tubing to restrict the flow through the tubing. These apparatus are commonly known as production chokes or more simply, chokes. The chokes are sized to limit flow through the tubing to a desired value. However, since the producing zones are often at very high pressure, the flow from the downstream end of the choke is usually at extremely high velocity. In many instances the high velocity flow causes abrasion and cutting of the surfaces it contacts. This is a serious problem where sand or other abrasive particles are present in the production fluids. The problem is especially troublesome in wellhead control apparatus which must often be located in a confined space thus making compact apparatus necessary. Generally Wellhead control apparatus, including wellhead manifolds and other choke boxes, have metal surfaces which are exposed to high velocity flow at the downstream end of a choke and these surfaces sufler from abrasion by the fluid.

The problem has been recognized in the art and attempts have been made to solve it. Devices known as flow targets have been placed in the path of the high velocity fluid stream to take the force of it. The flow targets hCI'BtOfOI'B used presented a relatively abrasionresistant surface to the high velocity stream. The abrasion-resistant surface deflected the stream and reduced its energy. Flow targets of this type are shown in US. PatentsNos. 2,590,688 and 2,943,640. Generally the flow target of the prior art comprised a body member having an insert for deflecting the fluid stream passing through the choke. The insert was made of abrasionresistant material such as lead, tungsten carbide or a ceramic. However, in field operation the flow targets heretotore known have not proved suitable because of the rapid abrasion and wear of the insert. This is especially true in producing from fields which flow a lot of sand in the produced petroleum fluids.

Briefly the present invention provides an improved flow target for a production choke comprising means forming a blind borehole, said blind borehole having a depth substantially greater than its diameter and a means for aligning the blind borehole in the flow path of the production choke to receive the high velocity fluid stream from the choke. The blind borehole retains a portion of the fluid from the fluid stream to serve as a cushion for the impinging stream. The energy of the high velocity stream is absorbed by the fluid cushion and abrasion of the surfaces of the flow target is prevented.

It is a particular object of this invention to provide an improved flow target for a production choke in wellhead control apparatus, which flow target makes use of fluid to cushion the impinging fluid stream from the choke.

Other objects and advantages of the present invention will be apparent from the following detailed description read in light of the accompanying drawings which are a part of this specification and in which:

FIG. 1 is a sectional view of one type of wellhead control apparatus showing the preferred embodiment of the flow target of the present invention.

FIG. 2 is a sectional view of the preferred embodiment of the apparatus of the present invention.

FIG. 3 is section 3-3 of FIG. 2.

With particular reference to FIG. 1, one type of apparatus for controlling the flow of petroleum fluids from a producing well is shown. The wellhead control apparatus shown in FIG. 1 is a wellhead manifold 60. The manitold 60 of FIG. 1 is a dual manifold useful in controlling flow from a well having more than one producing zone, and it is fully described in US Patent 2,943,640. A brief description of the manifold and its operation is useful in understanding the improvements provided by the present invention.

Generally when a production choke in included in wellhead control apparatus, a flow target is also used to receive the high velocity flow from the choke and to absorb the energy of the fluid stream. This is particularly true of wellhead control apparatus such as illustrated in FIG. 1 where close tolerances in the apparatus require conduits with sharp corners immediately after the choke. For eX- arnple, in FIG. 1 the flow of petroleum fluids enters manifold 6% from the well via appropriate tubing to passage 22. The petroleum fluids then enter duct 26 by way of passage 2 Valve stem 36 for seating in valve seat 32 controls flow in duct 2-6 between passage 24 and conduit 26. A choke 40 is positioned in conduit 20 to control the flow of fluid through conduit 20. A high velocity fluid stream results as the well fluids pass through the restricted opening of choke it) and enter the downstream portion of conduit 26. The pertoleum fluids strike the flow target of the present invention, which target is represented generally by the numeral M. The flow target 44 expends the energy of the high velocity fluid stream. The fluid leaves the wellhead control apparatus by means of duct 46 and conduit 48. Valve stem 5%) for seating in valve seat 52 controls flow of fluids leaving duct 46. The choke is cleaned or replaced by removing plug 55 to provide access to choke it in conduit 20.

It has been found that wellhead control apparatus is particularly vulnerable where a conduit makes a sharp turn immediately downstream of a choke. The high velocity fluids striking the corner a brade and cut away the surface. Heretofore flow targets have been used to deflect the fluid stream passing from the choke. These targets are expensive and are subject to rapid wear. The present invention provides an improved flow target generally represented as 44 in FIG. 1 which provides a fluid cushion for the impinging fluid stream passing from the choke.

Referring now to FIG. 2 and FIG. 3, a preferred form of apparatus according to the present invention will be more completely described. The present invention provides an improved flow target generally represented by 44 for wellhead control apparatus comprising means forming a blind borehole and means for aligning the blind borehole to receive high velocity fluid flow from a choke. In the preferred embodiment the means forming the blind borehole includes a plug 62. A blind borehole 61 extends interiorly of plug 62 a substantial distance from plug end 63. A preferred means for align-ingthe blind borehole .3 61 in position on wellhead control apparatus to receive high velocity flow from a choke is provided by flange 65. The flange is provided with suitable holes 66 for mounting on well control apparatus such as the well manifold of FIG. 1. The blind borehole 61 is alignable with the flow axis of the choke. When the plug 62 is mounted on the wellhead apparatus the longitudinal axis of the blind borehole 61 is aligned with the flow axis of the choke. If .the blind borehole is not aligned with the flow axis of the choke the fluid stream passing through the choke will not be cushioned in the blind borehole and damage to the flow target will occur. Packing 68 provides for a fluidtight seal when the flow target 44 is mounted on well control apparatus.

The blind borehole 61 extends interiorly of plug 62 from flanged end 63 a substantial distance. The longitudinal axis of the blind borehole is preferably identical to the longitudinal axis of plug 62 which forms it. The blind borehole is alignable with the longitudinal axis of the production choke. According to the present invention the blind borehole 61 must be of sufficient depth to provide a fluid cushion for the impinging fluid stream. In this manner abrasion which causes damage and wearing out of the metal surfaces of conventional flow targets is prevented. The blind borehole 61 must be proportionally long compared to its diameter to provide a sump for the temporary collection of a portion of the high velocity fluid entering it. The continually collected fluid then serves to cushion the later arriving high velocity fluid as it enters the blind borehole 61. The fluid in the blind borehole 61 absorbs the energy of the fluid stream and the flow target of the present invention is not subject to wear from abrasion.

According to the present invention the blind borehole must have a substantial depth compared to its diameter. The diameter of the blind borehole is preferably several times greater than the diameter of the restricted opening of the choke from which it receives a fluid stream. The diameter of the blind borehole is preferably less than the diameter of the conduit immediately downstream of the choke. The cross section of the blind borehole preferably is similar in shape to the cross section of the restricted opening of the choke. This is usually circular.

To provide a sump for the collection of fluid to serve as a fluid cushion for the impinging fluid stream the ratio of depth to diameter of the blind borehole must be at least 3 to 1. Best results are obtained when the proportion of depth to the diameter of the borehole is from about 4 to 1 to 5 to 1. The diameter of the blind borehole of the preferred embodiment of flow target is preferably constant. It has been found that a constant diameter hole provides a fluid cushion providing the hole is of adequate depth in relation to the diameter. It is not outside the limits of the present invention, however, to taper or to otherwise adjust the diameter of the hole as it progresses into the plug. The important test remains that hole configuration provide a sump for the collection of enough fluid to serve as a cushion to absorb energy from later arriving fluid passing from the choke.

It is an important aspect of the present invention that inserts of the type heretofore used in flow targets are unnecessary and are dispensed with by the improved flow target. However, it is within the scope of the present invention to provide an insert in the flow target body provided that the blind borehole has dimensions according to this specification. Generally, however, it is preferred to machine the flow target of the present invention from a single piece of stock and thus dispense with inserts of any type.

A demonstration to show the improved results of a flow target of the present invention compared to conventional flow targets, occurred in wells in the Gulf Coast area. The wells were producing through a production choke. The chokes were part of a wellhead manifold. The particular manifolds in use on these wells were Type 9080 Composite Manifolds manufactured by the Gray Tool Company of Houston, Texas. An improved flow target according to the present invention was installed in the positive choke section of the composite manifolds. The diameter of the blind borehole of the improved flow target was about 1 inch. The depth of the blind borehole was about 4 inches. After over nine months experimental operation the flow targets showed no signs of wear .and were in perfect condition for continued use.

In comparison with the excellent results achieved with the flow target of the present invention the history of conventional flow targets in the wells under substantially the same producing conditions is set out below.

Type of target insert: Must be replaced in As has been fully described and illustrated, the present invention provides an improved flow target for use with wellhead control apparatus. The invention is not to be limited to the specific examples set forth in this specification but only by the scope of the appended claims.

I claim:

1. A flow target for receiving high velocity fluid flow from a production choke in wellhead control apparatus comprising an elongated plug having an end for seating in said wellhead control apparatus, said plug having an elongated blind borehole extending interiorly of said plug from said end, the longitudinal axis of said blind borehole being alignable with the axis of said choke to receive the high velocity fluid flow from said choke, said blind borehole having an initial diameter substantially larger than the diameter of the restricted flow path in said choke and smaller than the flow conduit between said choke and the beginning of said blind borehole in said plug and said blind borehole having a depth at least three times greater than its said initial diameter.

2. For use in a wellhead that includes a fluid production choke to limit the flow rate through said wellhead, a flow target comprising a flange for mounting said target in the outlet path of fluid flowing through said choke, and means forming a blind borehole alignable with the axis of said choke, said borehole having a depth at least three times its diameter whereby a fluid cushion is formed by fluid in said blind borehole to absorb the energy of fluid passing through said choke.

3. A flow target for receiving high velocity fluid flow from a production choke in wellhead control apparatus comprising means forming a blind borehole, said blind borehole having a ratio of depth to diameter of at least 3 to 1, and means for mounting said blind borehole on said wellhead control apparatus in alignment with the flow path of said choke to receive high velocity fluid flow from said choke whereby a cushion of fluid is formed in said blind borehole to absorb the energy of said high velocity fluid flow.

4. A flow target as in claim 3 where the ratio of depth to diameter of the blind borehole is at least about 4 to 1.

5. A flow target for receiving high velocity fluid flow from a choke in wellhead control apparatus comprising an elongated plug having a flanged end for mounting in said wellhead control apparatus in the flow path of said choke, and a blind borehole extending interiorly of said plug from said flanged end, said blind borehole having its axis alignable with the flow axis of said choke and having a ratio of depth to diameter of at least about 3 to 1.

6. A flow target for absorbing the energy of fluid flow through a production choke in wellhead control apparatus comprising an elongated plug having a flanged end for seating on said wellhead control apparatus, said plug having a blind borehole alignable with the flow path of said choke and extending interiorly of said plug from said flanged end at least a distance equal to three times 5 the diameter of the opening of said blind borehole to provide a sump for the temporary collection of a portion of the fluid from said choke whereby the collected fluid forms a cushion to absorb the energy of the fluid flowing through said choke.

References Cited by the Examiner UNITED STATES PATENTS 610,066 8/98 Kuser 30264 XR Watts 16691 XR Knowlton 16691 James 137594 Pro 30259 Janssen 138178 ISADOR WEIL, Primary Examiner.

WILLIAM F. ODEA, Examiner. 

2. FOR USE IN A WELLHEAD THAT INCLUDES A FLUID PRODUCTION CHOKE TO LIMIT THE FLOW RATE THROUGH SAID WELLHEAD, A FLOW TARGET COMPRISING A FLANGE FOR MOUNTING SAID TARGET IN THE OUTLET PATH OF FLUID FLOWING THROUGH SAID CHOKE, AND MEANS FORMING A BLIND BOREHOLE ALIGNABLE WITH THE AXIS OF SAID CHOKE, SAID BOREHOLE HAVING A DEPTH AT LEAST THREE TIMES ITS DIAMETER WHEREBY A FLUID CUSHION IS FORMED BY FLUID IN SAID BLIND BOREHOLE TO ABSORB THE ENERGY OF FLUID PASSING THROUGH SAID CHOKE. 